Abstract
To determine whether sex differences exist in the pulmonary oxygen uptake (VO2) uptake on-kinetic response to moderate exercise in obese adolescents. We also examined whether a relationship existed between the VO2 on-transient response to moderate intensity exercise, steady-state VO2, and peak VO2 between obese male and female adolescents.Male (n = 12) and female (n = 28) adolescents completed a graded exercise test to exhaustion on a treadmill. Data from the initial 4 minutes of treadmill walking were used to determine the time constant.The time constant was significantly different (P = .001) between obese male and female adolescents (15.17 ± 8.45 seconds vs 23.07 ± 8.91 seconds, respectively). No significant relationships were observed between the time constant and variables of interest in either sex.Sex differences exist in VO2 uptake on-kinetics during moderate exercise in obese adolescents, indicating an enhanced potential for male subjects to deliver and/or use oxygen. It may be advantageous for female subjects to engage in a longer warm-up period before the initiation of an exercise regimen to prevent an early termination of the exercise session.

Abstract
Previous studies investigating acromioclavicular (AC) joint injuries in professional American football players have only been reported on quarterbacks during the 1980s and 1990s. These injuries have not been evaluated across all position players in the National Football League (NFL).The purpose of this study was 4-fold: (1) to determine the incidence of AC joint injuries among all NFL position players; (2) to investigate whether player position, competition setting, type of play, and playing surface put an athlete at an increased risk for this type of injury; (3) to determine the incidence of operative and nonoperative management of these injuries; and (4) to compare the time missed for injuries treated nonoperatively to the time missed for injuries requiring surgical intervention.Descriptive epidemiological study.All documented injuries of the AC joint were retrospectively analyzed using the NFL Injury Surveillance System (NFLISS) over a 12-season period from 2000 through 2011. The data were analyzed by the anatomic location, player position, field conditions, type of play, requirement of surgical management, days missed per injury, and injury incidence.Over 12 NFL seasons, there were a total of 2486 shoulder injuries, with 727 (29.2%) of these injuries involving the AC joint. The overall rate of AC joint injuries in these athletes was 26.1 injuries per 10,000 athlete exposures, with the majority of these injuries occurring during game activity on natural grass surfaces (incidence density ratio, 0.79) and most often during passing plays. These injuries occurred most frequently in defensive backs, wide receivers, and special teams players; however, the incidence of these injuries was greatest in quarterbacks (20.9 injuries per 100 players), followed by special teams players (20.7/100) and wide receivers (16.5/100). Overall, these athletes lost a mean of 9.8 days per injury, with quarterbacks losing the most time to injury (mean, 17.3 days). The majority of these injuries were low-grade AC joint sprains that were treated with nonoperative measures; only 13 (1.7%) required surgical management. Players who underwent surgical management lost a mean of 56.2 days.Shoulder injuries, particularly those of the AC joint, occur frequently in the NFL. These injuries can result in time lost but rarely require operative management. Quarterbacks had the highest incidence of injury; however, this incidence is lower than in previous investigations that evaluated these injuries during the 1980s and 1990s.

Abstract
Performing a single-bundle anterior cruciate ligament (ACL) reconstruction within the femoral footprint is important to obtain a functional graft and a stable knee.There will be a significant difference in the ability of 3 ACL reconstruction techniques to reach and cover the native femoral footprint.Controlled laboratory study.The percentage of the ACL footprint covered by the femoral tunnel was compared after 3 different techniques to target the footprint: transtibial (TT), inside-out/anteromedial (IO), and outside-in/transfemoral (OI). Fourteen cadaveric knee specimens with a mean age of 67.5 years were used. For each knee, the TT technique utilized a 7.5-mm offset guide, the IO technique was performed through an accessory anteromedial portal, and the OI technique was carried out through the femur from the external wall of the lateral condyle. Entry points in the footprint were spotted with markers, and orientations (sagittal and frontal) of each drill guide were noted. The distal femurs were sawed and scanned, and 3-dimensional image reconstructions were analyzed. The virtual drilled area (reamer diameter, 8 mm) depending on the entry point and the sagittal/frontal orientation of the drill guide was calculated and reported for each of the 3 techniques. The distance from the tunnel center to the ACL center, percentage of the femoral tunnel within the ACL footprint, and percentage of the ACL footprint covered by the tunnel were calculated and statistically compared (analysis of variance and t test).The average distance to the native femoral footprint center was 6.8 ± 2.68 mm for the TT, 2.84 ± 1.26 mm for the IO, and 2.56 ± 1.39 mm for the OI techniques. Average percentages of the femoral tunnel within the ACL footprint were 32%, 76%, and 78%, and average percentages of the ACL footprint covered by the tunnel were 35%, 54%, and 47%, for the TT, IO, and OI techniques, respectively. No significant difference was observed between the IO and OI techniques (P = .11). The TT approach gave less satisfactory coverage on all testing criteria.The IO and OI techniques allowed for creation of a tunnel closest to the ACL femoral footprint center. Despite this fact and even if the average percentage of the drilled area included in the femoral footprint was close to 80% for these 2 techniques, the average percentage of the ACL footprint covered by the tunnels was <55% for all 3 techniques. Coverage of the ACL footprint depended on the entry point, orientation, and diameter of the drilling but also on the size of the footprint.To improve the coverage of the native femoral footprint with a single-bundle graft, in addition to the entry point it may also be necessary to consider the orientation of the drilling to increase the dimensions of the area while respecting the anatomic constraints of the femoral bone and graft geometry.

Abstract
The management of anterior cruciate ligament (ACL) tears in growing patients must balance activity modification with the risk of secondary (meniscal and cartilaginous) lesions, and surgical intervention, which could adversely affect skeletal growth. Many ACL reconstruction techniques have been developed or modified to decrease the risk of growth disturbance. We have not found any description of ACL reconstruction using a single hamstring, short graft implanted into intraepiphyseal, retroreamed sockets. Our hypothesis was that the technique that we used restored the knee stability and did not cause any growth disturbances.We retrospectively studied 28 patients (20 boys, 8 girls) who presented with a unilateral ACL tear and open growth plates. We performed short graft ligament reconstruction with the semitendinosus folded into 4 strands around 2 polyethylene terephthalate tapes. The graft was implanted into sockets that were retroreamed in the femoral and tibial epiphysis and the tapes were fixed remotely by interference screws. After a minimum period of 2 years, we evaluated the comparative knee laxity, the radiographic limb morphology, the appearance of secondary lesions, and the functional outcomes using the Lysholm and Tegner scores. Comparative analyses were performed using the Student t test with subgroups depending on the type of fixation used.The mean age of the patients was 13 years (range, 9 to 15 y). The mean follow-up was 2.8 years (range, 2 to 5 y). The mean difference in laxity at 134 N was 0.3 mm, as determined using a GNRB arthrometer. No patients reported meniscal symptoms or degenerative changes. We found no angular deformity or leg length inequality. Two patients suffered a recurrent ACL tear.The preliminary results from this series are consistent with prior studies demonstrating that intraepiphyseal ACL reconstruction is a safe reliable alternative for the pediatric population.Case series; level of evidence 4.

Abstract
To determine the safety and efficacy of 2 intra-articular, fluoroscopically guided hylan G-F 20 injections for painful glenohumeral osteoarthritis.This study was a prospective open-label pilot investigation with both U.S. Food and Drug Administration and institutional review board approval.Private, outpatient practice within a tertiary care, university medical school.Thirty-six subjects with moderate to severe glenohumeral osteoarthritis, with pain (visual analog scale [VAS] 40 mm or greater) despite following a 3-month standard, nonsurgical treatment program.Two injections of 2 mL hylan G-F 20, under fluoroscopic guidance confirmed by arthrography, 2 weeks apart. No new treatments were allowed during the course of the study. Analgesics were discontinued 24 hours before visits.Data collected were radiographs; rotator cuff integrity as determined with magnetic resonance imaging; VAS for pain at rest, at night, and with activity; and shoulder-related quality of life (Western Ontario Rotator Cuff Index [WORC]). Subjects were re-evaluated after each injection and at 6 weeks, 3 months, and 6 months. Changes from baseline for VAS and WORC were recorded in Excel and analyzed using SPSS. Intent-to-treat analysis was performed. The type and severity of adverse events were recorded.Mean VAS at baseline was 63 mm (SD 14.5). Clinically (>or=20% improvement) and statistically significant improvements (P < .001) in VAS pain were seen at 6 weeks, 3 months, and 6 months. Mean improvement in WORC at 6 months was 16.5 (P < .01), with most gains in "lifestyle" and "emotion" questions. Age, gender, body mass index, and rotator cuff pathology did not correlate with response. Three subjects described heightened pain for a few days after injections. Three subjects reported greater pain at 6 months and were unsatisfied. Four experienced no effect of treatment. There were no inflammatory reactions.Two hylan G-F 20 injections improved pain and function, and should be considered as part of a multimodal shoulder osteoarthritis treatment program.

Abstract
Injuries and conditions that affect the AC joint are common. Low-grade separations, degenerative conditions, and osteolysis of the distal clavicle are frequently dealt with by the treating physician. Proper assessment requires a thorough history, examination, and radiologic work-up. An injection of bupivicaine into the AC joint can be a very useful test to evaluate the source of pain about the symptomatic shoulder. Most conditions affecting the AC joint can be treated conservatively, but patients who do not respond to these treatments or athletes who do not wish to modify their activities may require resection of the distal clavicle and the AC joint. Operative intervention can be performed as an open procedure with good results. Recent advances in operative arthroscopic procedures allow us to replicate and exceed the results of the open resection. Arthroscopic resection can be undertaken via a direct approach that does not violate the subacromial space or via an indirect or bursal approach. The indirect approach allows you to assess both the subacromial space and the AC joint because impingement pathology and subacromial compromise are frequently associated with AC change. The advantage of an arthroscopic resection is its ability to be performed as an outpatient procedure with less compromise of musculotendinous structures, shorter rehabilitation, and quicker return to activity. The amount of bone resection necessary is less than with the open procedure because of the ability to preserve the stabilizing properties of the superior AC ligaments. Resection of 4 mm to 8 mm of bone is all that may be required to give uniformly good results. Arthroscopic resection of the distal clavicle is technically demanding and requires skill and familiarity with other arthroscopic shoulder procedures. Complications related to this procedure are relatively infrequent and include infection, residual pain, lack of adequate bone resection, and instability, particularly in patients with previous grade 1 and 2 separations. Less commonly noted is the symptomatic development of heterotopic bone. To the accomplished arthroscopic shoulder surgeon, arthroscopic resection of the symptomatic AC joint gives excellent clinical results that allow a compromised athlete a relatively quick return to desired sport activities.

Abstract
It is unclear how muscle strength in tibial rotation and knee abduction change following anterior cruciate ligament (ACL) injury and reconstruction. Such strength changes are likely, considering the oblique orientation of the ACL and the constraint provided by the ACL at various tibial rotation and adduction positions. The purposes of this study were to evaluate multiaxis muscle strength in ACL deficient and reconstructed knees and to gain insights into potential compensatory mechanisms adopted by the patients.Muscle strength in tibial internal-external rotation, abduction-adduction, and flexion-extension were investigated in 19 chronic ACL deficient, 18 acute ACL deficient, 21 ACL reconstructed, and 23 normal subjects. The strength ratios of flexion/extension, abduction/adduction, and internal/external rotation were determined for each subject and compared across the different populations.The chronic ACL deficient patients showed significantly lower strength ratio in internal/external rotation than that of the normal controls and acute ACL deficient subjects (P = 0.02), indicating a compensatory mechanism developed by the patients to unload the ACL and/or to avoid unstable knee positions. For ACL reconstructed patients, the internal/external rotation strength ratio became closer to their counterparts in normal controls than that of chronic ACL deficient patients, presumably reflecting the reduced need for compensation after reconstruction. Furthermore, compared with strength reduction in knee extension, reductions in tibial rotation and abduction strength following ACL reconstruction were less severe and more easy to recover.A better understanding of changes in multiaxis muscle strength and the associated compensatory mechanism will help us evaluate treatment outcome more accurately and develop more effective treatment modalities with focus on muscles that help protect and unload the ACL.

Journal of orthopaedic research : official publication of the Orthopaedic Research Society 2000 Jan

Authors:
Zhang LQ,

Abstract
To evaluate the dynamic properties of the shoulder and understand how they are controlled by the central nervous system, glenohumeral-joint stiffness and viscosity and upper-limb inertia were quantified under various levels of muscle contraction in seven healthy human subjects. Through a cast attachment, the upper limb was perturbed in a precise pattern by a computer-controlled servomotor to manifest the dynamic properties of the joint. The recorded joint position and torque were used to estimate joint stiffness and viscosity and upper-limb inertia. With moderate muscle contraction, the stiffness and viscosity increased several fold. A stiffer shoulder joint associated with stronger muscle contraction made the shoulder more stable and protected it from potential injuries during strenuous tasks. Joint viscosity, especially the stronger viscous damping associated with more strenuous contraction, smoothed shoulder movement and stabilized the joint. From the control viewpoint, the glenohumeral joint responded to the central nervous system more quickly with increasing muscle contraction, which was useful during strenuous tasks. On the other hand, the central nervous system controlled stiffness and viscosity synchronously so that it dealt with only a nearly constant damping ratio of the joint over various levels of contraction, which simplified its task substantially. This approach quantified the dynamic and static properties of the shoulder under various levels of contraction more accurately and completely than a manual test, and it can potentially be used to evaluate changes in these properties caused by musculoskeletal injuries and their surgical treatments.

Arthroscopy : the journal of arthroscopic & related surgery : official publication of the Arthroscopy Association of North America and the International Arthroscopy Association 1999 Oct

Authors:
Anderson K,

Abstract
Rotator cuff pathology has been associated with a hooked acromial morphology. Impingement syndrome has traditionally been considered to be the result of bony encroachment into the subacromial space. This report of a spur recurrence after acromioplasty presents evidence that acromial morphology may be a reactive change attributable to primary rotator cuff insufficiency.

Jan 2014

Dr. Mark Bowen, orthopedic surgeon with NorthShore University HealthSystem, says there are many activities people engage in that get them into trouble with their knees, and specifically ACL injuries...

Mar 2012

NorthShore University HealthSystem orthopaedic surgeon Mark Bowen, MD, is one of the original and now growing number of surgeons in the US performing this technique, which was invented in Belgium and developed in France...